Effects of different types of flame-retardant treatment on the flame performance of polyurethane/wood-flour composites

To improve the flammability of foamed polyurethane/wood-flour composites (FWPC), ammonium polyphosphate (APP) was used as a flame retardant to modified FWPC. The effects of different flame treatment processes on flame performance, smoke suppression, thermal property, and surface micrographs of flame retardant FWPC were investigated. The results showed that FWPC with the addition or impregnation process both improved the combustion behaviors. Compared with the addition process, FWPC-impregnation (FWPC-I) had a lower total heat release (THR), lower peak heat release rate (PHRR), prolonged time to ignition (TTI), more residues, and better combustion safety. FWPC-I had the highest residual carbon rate reaching 39.98%. A flame-retardant layer containing the P-O group was formed in the residual carbon of FWPC-I. Although APP had negative effects on the physical properties of FWPC, it was an effective flame-retardant ability for foamed polyurethane/wood-flour composites.

Ramie fiber reinforced composites with flame retardant structure design: flammability, smoke suppression, and mechanical properties

In this work, the structure of composite was designed as Core Stack and Surface Stack, which was treated with the expandable graphite (EG) and metal oxides such as iron oxide (IO), hydroxyapatite (HA), and aluminum tri-hydroxide (ATH). The mechanical performance of composites was characterized via flexural performance and interlaminar shear strength analysis. The flame retardance and smoke suppression of composite was explored in detail by LOI, UL-94, and cone calorimeter test. The findings presented that flexural properties of composites were observed to decrease due to delamination of surface stack, whilst no significant effect on interlaminar shear strength. In comparison with control composite, the loading of metal oxide into composite Surface Stack led to the reduction of peak heat release rate, total heat release, and fire growth index effectively. Moreover, the remarkable decrease in total smoke production could be observed due to the addition of iron oxide and the flame retardant mechanism was discussed. This study was the preliminary exploration of composite with flame retardant design which could be potential solution to improve flame retardancy and smoke suppression of composite with better mechanical structure preservation.

Synergistic Flame Retardant Effect of Barium Phytate and Intumescent Flame Retardant for Epoxy Resin

Recently, widespread concern has been aroused on environmentally friendly materials. In this article, barium phytate (Pa-Ba) was prepared by the reaction of phytic acid with barium carbonate in deionized water, which was used to blend with intumescent flame retardant (IFR) as a flame retardant and was added to epoxy resin (EP). Afterward, the chemical structure and thermal stability of Pa-Ba were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), respectively. On this basis, the flammability and flame retardancy of EP composites were researched. It is shown that EP/14IFR/2Ba composite has the highest limiting oxygen index (LOI) value of 30.7%. Moreover, the peak heat release rate (PHRR) of EP/14IFR/2Ba decreases by 69.13% compared with pure EP. SEM and Raman spectra reveal the carbonization quality of EP/14IFR/2Ba is better than that of other composites. The results prove that Pa-Ba can cooperate with IFR to improve the flame retardancy of EP, reducing the addition amount of IFR in EP, thus expanding the application range of EP. In conclusion, adding Pa-Ba to IFR is a more environmentally friendly and efficient method compared with others.

Design and characterization of ramie fiber-reinforced composites with flame retardant surface layer including iron oxide and expandable graphite

The ramie plain-woven fabric-reinforced epoxy composites with iron oxide (IO) powders and expandable graphite (EG) particles were fabricated by the hand lay-up and vacuum bagging pressing. The flame retardant layers with IO powders and EG particles have been designed on the surface of the composite structure, to improve the composites flame retardancy. The flame retardancy property of the composites was discussed from the limited oxide index (LOI), vertical burning test, and cone calorimeter test, while the flexural property and interlaminar shear strength of the composites were also investigated through the three-point flexural tests, respectively. It was found that the flame retardancy property of the composites, which contains both IO powders and EG particles, can be greatly improved. However, IO powders and EG particles have a negative effect on flexural properties and interlaminar shear strength of the composites. Also, prepreg with IO powders or EG particles which laminated on the surface layer of the composite with different orders would result in different performances.

Mesoporous silica via self-assembly of nano zinc amino-tris-(methylenephosphonate) exhibiting reduced fire hazards and improved impact toughness in epoxy resin

Mesoporous silica@nano-zinc amino-tris-(methylenephosphonate) (m-SiO₂@Zn-AMP) spheres were synthesized via a self-assembly process to integrate the outstanding flame retardancy, thermal stability, and mechanical properties of these materials. The results indicated that nano Zn-AMP particles were successfully deposited on the surface of m-SiO₂ through electrostatic interactions. The prepared m-SiO₂@Zn-AMP was utilized to improve the flame retardancy, smoke suppression, and mechanical properties of epoxy resin (EP). The storage modulus, impact, and tensile strengths of the EP with 1% m-SiO₂@Zn-AMP (sample EP/1m-SiO₂@Zn-AMP) were increased by 29.9, 50.0, and 23.5 %, respectively, relative to the values for untreated EP. The presence of multiple flame retardant elements (i.e. Si, P, N, and Zn) in the mesoporous spheres led to the formation of high yields of compact char residues and the release of inert substance during combustion, for high flame retardancy and efficient smoke suppression in the condensed and gaseous phase. The EP/5m-SiO₂@Zn-AMP sample achieved a V0 rating in a vertical UL-94 test. Compared to untreated EP, the amount of total smoke released and the peak CO production rate of EP/5m-SiO₂@Zn-AMP were reduced by 53.1 and 61.5 %, respectively. Additionally, the total heat release and peak heat release rate of EP/5m-SiO₂@Zn-AMP were decreased by 45.2 and 57.8 %, respectively.

Facile preparation of magnetic porous carbon monolith from waste corrugated cardboard box for solar steam generation and adsorption

Porous carbon monoliths (PCMs) were prepared from waste corrugated cardboard box (WCCB) via slurrying in FeCl₃ solution followed by molding and thermal treatment. The thermal process was analyzed by a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. The evolution of physicochemical characteristics of PCMs was studied. The photothermal conversion and solar steam generation performances of the optimal sample (PCM_Fe/600) were evaluated. The adsorption properties of PCM_Fe/600 for methylene blue (MB) were investigated. Results showed that Fe³⁺ promoted the breaking of cellulose chains in WCCB, leading to the occurrence of pyrolysis of WCCB at lower temperatures and the reduction of activation energy by 76.63 kJ mol^-1. Char yield raised because volatile radicals were captured by FeCl₃-derived amorphous Fe(III) species, then involved in char formation. Amorphous Fe(III) continuously converted into Fe₃O₄ crystallites with carbonization temperature increasing from 400 to 700 °C, then α-Fe was formed at 800 °C via the carbothermal reduction of Fe₃O₄. FeCl₃ was favorable to the formation of a developed microporous structure. Surface area significantly increased with carbonization temperature increasing from 400 to 600 °C due to the removal of volatiles. The etching of carbon by Fe₃O₄ above 700 °C also led to the increase of surface area. PCM_Fe/600 exhibited higher optical absorption than other samples due to its high graphite degree and porosity. It also had excellent photothermal performance; thus, solar steam yield was 1.46 times that of the pure water with the assistance of PCM_Fe/600. PCM_Fe/600 in floating state was effective in adsorption of MB from water. Besides, the adsorption behavior fitted Langmuir model with a monolayer adsorption capacity reached up to 70.9 mg g^-1.

Flame Retardant Epoxy Composites on the Road of Innovation: An Analysis with Flame Retardancy Index for Future Development

Nowadays, epoxy composites are elements of engineering materials and systems. Although they are known as versatile materials, epoxy resins suffer from high flammability. In this sense, flame retardancy analysis has been recognized as an undeniable requirement for developing future generations of epoxy-based systems. A considerable proportion of the literature on epoxy composites has been devoted to the use of phosphorus-based additives. Nevertheless, innovative flame retardants have coincidentally been under investigation to meet market requirements. This review paper attempts to give an overview of the research on flame retardant epoxy composites by classification of literature in terms of phosphorus (P), non-phosphorus (NP), and combinations of P/NP additives. A comprehensive set of data on cone calorimetry measurements applied on P-, NP-, and P/NP-incorporated epoxy systems was collected and treated. The performance of epoxy composites was qualitatively discussed as Poor, Good, and Excellent cases identified and distinguished by the use of the universal Flame Retardancy Index (FRI). Moreover, evaluations were rechecked by considering the UL-94 test data in four groups as V0, V1, V2, and nonrated (NR). The dimensionless FRI allowed for comparison between flame retardancy performances of epoxy composites. The results of this survey can pave the way for future innovations in developing flame-retardant additives for epoxy.

The synergistic effect of cuprous oxide on an intumescent flame-retardant epoxy resin system

Neat epoxy resin (EP) is a highly flammable material, and the pyrolysis volatiles of it contain some harmful gases such as carbon monoxide, aromatic compounds, hydrocarbons, etc.

Scalable Preparation of Multifunctional Fire-Retardant Ultralight Graphene Foams

Traditional flame-retardant materials often show poor tolerance to oxidants, strong acidic/alkaline reagents, organic solvents, along with toxicity problems. Herein, highly fire-retardant ultralight graphene foam has been developed, which possesses not only ultralight and compressible characteristics but also efficient flame-retardant properties, outperforming those traditional polymer, metallic oxide, and metal hydroxide based flame retardant materials and their composites. The newly developed unconventional refractory materials are promising for specific applications as demonstrated by the observed high temperature resistant microwave absorption capability.